Today's offshore industry requires a great deal of subsea completions. Especially, the subsea power distribution systems to and between e.g. oil platforms or other offshore power consumers, include a lot of relatively large and heavy components, such as transformers.
The installation process of these components may be both complicated and demanding because of the strong and unpredictable environment the installers encounter. Additionally, the installers have less control over the components because the installation often has to be done remotely, e.g. from a boat. Thus, during the process, there is a considerable risk of damaging the components, and if the installation fails, there are often limited possibilities for correction.
Installation of transformers used in subsea power distribution systems is an example of such a risky installation process. A common technique when installing subsea transformers is to slowly lower the transformer from e.g. a boat, towards a foundation localized on some desired place at the bottom of the sea. Conventionally, transformers are rectangular shaped, and proper placement is ensured by means of two or four guide pins positioned at the edges of the foundation. The guide pins are adapted to fit into some funnels positioned at the transformer's edges such that when the funnels enter all the guide pins, the transformer is meant to be secured a correct position and orientation.
The main drawback of the installation process mentioned above is that large objects, in particular rectangular ones, are widely exposed to underwater currents when being lowered. Experience has shown that they tend to twist around during deployment, especially in depths where guide wires are not used. This fact makes it difficult to enter the guide pins with the funnels placed at the edges of the transformers, all at the same time.
Moreover, even if the installation apparently has succeeded, the orientation of the transformer may differ 90 or 180 degrees from the correct orientation, if the guide pins have been entered in wrong funnels.
A further drawback is that the transformer risks to jam/wedge between the guide pins, if the installation fails. This may cause damage, or even loss, of the transformer which is to be installed.
Moreover, the transformer may be overturned by the guide pins when sighting the transformer, and this may also cause damage or loss.